Rigorous design of an ultra-high Q/V photonic/plasmonic cavity to be used in biosensing applications

• A device based on a PhC dielectric cavity coupled to a plasmonic slot is proposed.
• The design of the device was carried out by using the 3D Finite Element Method.
• A Q/V ratio=107(λ/n)−3 was achieved due to the high confinement in the cavity.
• The strong light-matter interaction makes the hybrid cavity suitable for biosensing.

A hybrid device based on a 1D PhC dielectric cavity vertically coupled to a plasmonic slot is proposed for use in biosensing applications. Under efficient coupling conditions between the Bloch mode in the 1D PhC dielectric cavity and the surface plasmon polaritons mode in the metal slot, an ultra-high Q/V ratio (~107(λ/n)−3) has been achieved with a remarkable resonance transmission T (=47%), due to high spectral and spatial confinement in the cavity. The rigorous design process of the cavity, including the influence of geometrical and physical parameters on its performance, has been carried out using the 3D Finite Element Method. A strong light-matter interaction was observed, making the photonic-plasmonic cavity suitable for biosensing and, in particular, for optical trapping of living matter at nanoscale, such as proteins and DNA sections, as required in several biomedical applications.